Metabolically assessed muscle fibre recruitment in brief isometric contractions at different intensities

Beltman, J. G. M., de Haan, A., Haan, H., Gerrits, H. L., van Mechelen, W. and Sargeant, A. J. (2004) Metabolically assessed muscle fibre recruitment in brief isometric contractions at different intensities. European Journal of Applied Physiology, 92 4-5: 485-492. doi:10.1007/s00421-004-1105-6


Author Beltman, J. G. M.
de Haan, A.
Haan, H.
Gerrits, H. L.
van Mechelen, W.
Sargeant, A. J.
Title Metabolically assessed muscle fibre recruitment in brief isometric contractions at different intensities
Journal name European Journal of Applied Physiology   Check publisher's open access policy
ISSN 1439-6319
1439-6327
Publication date 2004-08-01
Sub-type Article (original research)
DOI 10.1007/s00421-004-1105-6
Open Access Status
Volume 92
Issue 4-5
Start page 485
End page 492
Total pages 8
Place of publication Heidelberg
Publisher Springer Berlin
Language eng
Subject 1103 Clinical Sciences
Formatted abstract
This study investigated the recruitment of type I, IIA and IIAX fibres after seven isometric contractions at 40, 70 and 100% maximal voluntary knee extension torque (MVC, 1 s on/1 s off). Biopsies of the vastus lateralis muscle were collected from seven subjects at rest and immediately post-exercise.

Fibre fragments were dissected from the freeze-dried samples and characterized as type I, IIA and IIAX using mATPase staining. Phosphocreatine (PCr) and creatine (Cr) content were measured in the remaining part of characterized fibres.

A decline in the ratio of PCr to Cr (PCr/Cr) was used as an indication of activation. The mean peak torques were, respectively, 39 (2), 72 (2) and 87 (6)% MVC. Cumulative distributions of type I and IIA fibres were significantly shifted to lower PCr/Cr ratios at all intensities (Kolmogorov-Smirnov test, P<0.05).

The cumulative distribution of type IIAX fibres showed a significant leftward shift only at 87% MVC (P<0.05). A hierarchical order of fibre activation with increasing intensity of exercise was found, with some indication of rate coding for type I and IIA fibres. Evidence for activation of type IIAX fibres was only found at 87% MVC.
Keyword Metabolism
PCr/Cr ratio
Quadriceps
Q-Index Code C1
Additional Notes Accepted: 5 March 2004 Published online: 8 May 2004

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
School of Human Movement and Nutrition Sciences Publications
 
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